Wednesday, September 28, 2011

Soldier flies, family Stratiomyidae, are so name because of the bright, almost militaristic colours of their body parts. Over 2800 species are described worldwide, varying widely in appearance, ranging in size from 3 to 30mm, possessing spines on the scutellum numbering from zero to eight, and bearing colors of metallic green, red, yellow, and black (1). Thirty two species are recorded in Ireland (2). Of these, one of the largest and certainly most attractive is the Two Spotted Centurion (Sargus bipunctatus). Ranging in size from 11 to 14 mm, there is pronounced sexual dimorphism between sexes. Males are are bright green, while the femals have an intense brown-red abdomen (3). Males and females have two white spots on their heads. Both adult forms can be seen on the wing from early July to late October (4), but rarely after mid October: larvae are to be found in dung compost and other rotting material, where they feed on detritus (5).

Some ferns are quite similar. The small filmy ferns Wilson's Filmy Fern (Hymedophyllum wilsonii) and Tunbridge Filmy Fern (H. tunbrigense) are virtually identical at first glance, with subtle features like the presence or absence of toothed edges on the scales protecting the sori having to be examined to differentiate them. One fern that doesn't have that problem though is the Royal Fern, Osmunda regalis. A strikingly distinctive fern, found in wet bogs and fens throughout Ireland (with a global distribution spanning Europe, Asia and Africa) its fronds can reach heights of 160 cm (1). Most of these are sterile, with the fertile fronds rising above the others in the centre of the plant. Their shuttlecock-like appearance and the fern's overall imposing height are unmistakable.

The Royal Fern, Osmunda regalis

Or are they? Homosporous ferns have two free-living generations, the sporophyte generation which is what most people would call the fern, and the relatively short lived gametophyte generation. The gametophyte generation is much smaller and shows far less morphological complexity. This means that identification is often next to impossible. Identification of fern gametophytes is important as they play an important part in fern dispersal and ecology. This problem has been overcome by the use of DNA-based identification. A sample of a gametophye in cultivation that was unknown for 30 years was identified as O. regalis using plastid sequencing (2). The gameteophyte never produced antheridia, and so never produced the sporophyte stage, and morphological analysis was inconclusive. Its identification as O. regalis shows the power of DNA-based techniques in revealing more about the ecology of fern gametophytes.References:

One of the most striking examples of convergent evolution I have come across is that of the Pill Millipede (Glomeris marginata) and the Pill Woodlouse (Armadillidum vulagre). Convergent evolution describes the acquisition of the same biological trait in unrelated lineages (1), and in both these animals the architecture of their exoskeleton allows them to curl into a ball (or “pill”) when alarmed. Closer examination of both species shows they are obviously not related, the most distinguishing feature being that G. marginata has two pairs of legs per segment, and many more to boot than the seven pairs possessed by A. vulgare. G. marginata also has shorter antennae and its dorsal plates are edged with cream rims. It can be found in leaf litter in mature woodlands (2), whereas A. vulgare is far more common - individuals can often be happened upon in urban gardens.

However, G. marginata may have further features, that show its apparent relatedness to insects, that are a result of convergence. Traditionally, morphological features such as loss of second antennae, formation of Malpighian tubules, postantennal organs and trachea have indicated that the myriapods are close relative to the insects (3). Yet these features have been shown to be prone to convergence (4), and molecular evidence also points to a far more distant relationship than previously thought. Of the four extant arthropod subphyla, the hexapoda and crustaceans are now seen as sister groups and mitochondrial genome analysis has revealed the same to be true for the myriapods and the chelicerates (5). This is backed up further by 18S/28S rRNA sequences and Hox gene analysis of the myriapods (3)

Overturned Pill Millipede (Glomeris marginata)

Analysis of neurogenesis in G. marginata has provided morphological evidence to support these claims (3). In the development of neuroblasts in G. marginata, groups of cells invaginate to form the the ventral neuroectoderm. This is similar to neurogenesis in spiders, but quite different than that in insects where single cells give rise to the neuroectoderm.

Friday, September 23, 2011

Schreckensteinia festaliella is the only member of the bristle leg moths, family Schreckensteiniidae, to occur in Europe, and only one of five species in whole the family. Although it is a small (c. 10 mm) moth, it has a fearsome common name: the Blackberry Skeletoniser. Putting one in mind of a character from the 1980's cartoon serial 'He-Man', it gets this name from the larvae's feeding habits on blackberry and other Roseacea species (1). Attacks can lead to extreme damage, leaving nothing but skeletons of leaves on plants, hence the name. However, only one case of severe damage to cultivated crops has been noted, that of Raspberries in Scotland (2).

The Blackberry Skeletoniser, Schreckensteinia festaliella, in distinctive repose with hind leg raised. Note the spines on the hind leg.

The bristle leg moths get their name from the quite large spines that occur on the hindmost legs. The slender winged adults are may be seen in repose with, quite distinctively with their hind legs raised and projected over the abdomen. Although native to Europe, S. festaliella was introduced to North America between 1963 and 1969 to control invasive wild blackberry (Rubus argutus) (3).

Spleenwort, Liverwort, Toothwort: seemingly picaresque names for common plants, their origin is actually based in an ancient concept of medicine, the Doctrine of Signatures. The early botanist – and all-round occultist – Paracelsus von Hohenheim (1493-1541) was the first to expand on ideas from antiquity and early European Christianity as the Doctrine of Signatures (1). The central tenet of the doctrine was that the shape, colour and other attributes of a plant indicated its use in healing. So the liver-shaped thallii of the Liverwort genus Marchantia spp. are, according to the doctrine, useful for treating liver ailments*. The Doctrine of Signatures was based on the belief that God marked all his creations with a sign, or signature. The sign showed its purpose. Its rise in popularity during the 15th and 16th centuries is rooted in the role 'resemblance' played in Western culture at that time.

Tree Lungwort, Lobaria pulmonaria

While the Doctrine of Signatures has long been rejected by botanists and chemists on the basis of scientifically controlled data, it has left us with a plethora of colourful names. However, one of these is, in a way, well deserved. Tree Lungwort (Lobaria pulmonaria) is an impressively large lichen that has the green alga Dictyochloropsis reticulata as its photosynthetic partner (2). It is found attached to the bark of trees in old to ancient woodlands with high levels of rainfall (3). While the pitted appearance of the thallii resemble lung tissue, the name 'Lungwort' is appropriate in another sense. Found in moderate regions of the tropics and throughout boreal regions of the norther hemisphere, it thrives in places of low pollution and has dissappeared entirely in parts of Central Europe in the 20th century due to falling air quality (4). Pollutants in the atmosphere condensing to form acid rain fall on the forests. L. pulmonaria colonise drainage channels below old and large wounds on deciduous trees. These channels are richer in minerals and had a higher pH than normal bark (5), but concentrate pollutants in rain. Populations of the lichen are thus wiped out

Tree Lungwort, Lobaria pulmonaria showing fruiting bodies

While the effect of L. pulmonaria on the lungs has yet to be proven, it has been shown to have some pharmacological properties (6). Liquid extracts from the lichen tested on rats showed moderate anti-inflamatory and strong antiulcerogenic affects.

*Note: The suffix 'wort' is derived from the old English word for plant.

Wednesday, September 21, 2011

The Orthoptera are the grasshoppers, groundhoppers and crickets. Twelve species are found in Ireland and regarded as native (1). Throughout the 19th and 20th centuries, a lack of attention was paid to Irish Orthoptera, with a few exceptions (2). Therefore the true extent of distribution of species may not reflected in the literature.

Irish Orthoptera Species

Family

Species

Common Name

Note

Tettigoniidae (Crickets)

Conocephalus dorsalis

Short Winged Cone Head

First recorded in 1989

Leptophyes punctatissima

Speckled Bush Cricket

Found in south

Meconema thallsainium

Oak-Bush Cricket

Found in south-west

Metrioptera roeselii

Roesel's Bush Cricket

First recorded in 1977

Pholidoptera griseoaptera

Dark Bush Cricket

First recorded in 1983

Tetrigidae (Groundhoppers)

Tetrix undulata

Common Ground Hopper

Widespread

Tetrix subulata

Slender Ground Hopper

Restricted to Galway

Acrididae (Grasshoppers)

Myrmeleotettix maculatus

Mottled Grasshopper

Widespread but local

Chorthippus brunneus

Common Field Grasshopper

Widespread

Chorthippus albomarginatus

Lesser Marsh Grasshopper

First recorded in 1960

Omocestus viridulus

Common Green Grasshopper

Widespread

Stethophyma grossum

Large Marsh Grasshopper

Found in west

Five species of grasshopper are present in Ireland (see table). Chorthippus brunneus and Omocestus viridulus are the most common, both being found in a variety of grassy places (3). Myrmeleotettix maculatus prefers drier areas such as dunes and heaths and therefore tends to be more local. Ireland's largest grasshopper, Stethophyma grossum, is locally restricted to floating acid bogs in the West of Ireland. C. albomarginatus is the most recent addition to the Irish grasshoppers, with a first record in 1960 (2). It is restricted to a few site in the south-west, favouring grassland and dunes.

Common Green Grasshopper, Omocestus viridulus

The grounhoppers are a family of orthopterans that resemble grasshoppers, but are much smaller in size. Unlike other Orthoptera, most groundhoppers overwinter as adults. Two species are present in Ireland. Tetrix undulata is of widespread but local occurence. T. subulata is similar in appearance, but has a longer protonum and wings and is restricted to Galway.
Crickets in Ireland are less common than grass- or groundhoppers. Five species of crickets are present in Ireland, with three of these being first recorded only in the last 34 years. Leptophyes punctatissima can be found in hedgerows but is restricted to the local areas in the south of Ireland and quite scarce. Meconema thallsainium is again restrcited to the south west of the country, favouring woodlands, but may also be seen sometimes in gardens. Found in damp meadows, Metrioptera roeselii was first recorded in 1977 (2). Pholidoptera griseoaptera was first recorded in Ireland in 1983 in the south east (4). it is found in in hedgerows and amongst scrub near sea cliffs and dunes. The most recent addition to the list of Irish orthopera is Conocephalus dorsalis. This was recorded in 1989 in the south west prefers two distintct habitats: coastally on saltmarshes and sand dunes and inland on lowland bogs and fens.

Common Field Grasshopper, Chorthippus brunneus

As well as frequent records of one-off species arriving on imported produce, three other orthoptera species of note have been recorded in Ireland. The European Mole Cricket, Gryllotalpa gryllotalpa, was recorded in from one site in Northern Ireland pre 1970, but is not considered native. The non-native House Cricket Acheta domesticus was present in Ireland until about 1960, but although recent sightings have been reported (5), it is now considered rare or absent. The Greenhouse Camel Cricket, Tachycines asynamorus can be found as an introduced species in Ireland, but as it tends to become established in artificial situations such as greenhouses, it is not included in the Irish list of Orthoptera.

Tuesday, September 20, 2011

The Velvet Swimming Crab (Necora puber) is unique in a couple of senses. Firstly, it is the only member of the genus Necora, having been classified as such following reexamination of type material in 1987 (1). Secondly it, unusually for a swimming (or portunid) crab, occurs predominantly on hard substrates (2). It is also the largest swimming crab to be found in the waters surrounding Ireland and Britain, its final pair of pereiopods being flattened, fin-like to aid swimming. However its most striking features are its red eyes (lending it the alternative common name, “Devil Crab) and its velvety appearance. This is due to tiny hairs covering the carapace and appendages which allow a layer of algae to cover the crab. An important commercial crab (3), N. puber is usually found in shallow water to a depth of 20 m where it feeds on a variety of organisms including other crustaceans, molluscs and brown algae.

Velvet Swimming Crab, Necora puber, with swimming pereiopod on right

Interaction between individual crabs are more often than not antagonistic, with fights occurring between all sizes of crabs. They seem to prefer a solitary lifestyle and it is assumed that this is because large numbers of crabs increase the presence of predators and competition for food (4). In laboratory conditions (4), N. puber individuals were seen surprisingly not to engage in an escalation of violence, but rather in sporadic bursts. Fights between individuals were won in the majority of cases by the larger crab, yet smaller crabs never backed down from confrontation. This might seem a bit foolhardy on their parts, having little chance of winning, but under the laboratory conditions all crabs were in intermoult stage and had a hard outer shell. In vivo, fights may be one by smaller crabs against larger but softer ones.

When it comes to species under threat, its the specialists that seem to be in the most trouble. Relying on, say, a single rare plant species for food or existing only in a specific microhabitat spells trouble in the extinction stakes. Yet the news is seemingly equally as grim for some widespread species.

Small Copper Butterfly, Lycaena phlaeas

The Small Copper (Lycaena phlaeas) is a common butterfly of hedgerows and woodland verges in Ireland, although it is also frequently spotted in fields and even gardens. It is considered common throughout Europe, Asia, North America and even north Africa, feeding on Common Sorrel (Rumex acetosa) and other Rumex spp. (1). However a detailed study of numbers in north Wales showed a population level decline of 89%, a level comparable to that of species considered rare and threatened (2). Habitat loss and fragmentation are the causes of the reduction in numbers. This illustrates the difficulty in foreseeing what consequences our further misuse of natural resources will have on a range of species.

With its sprigs of purple flowers on stalked shoots, Sea Lavender (Limonium humile) does indeed resemble its namesake Lavender (Lavandula spp.). Its there though that the similarity ends, as the resemblance is superficial with no relationship existing. L. humile can be found growing, sometimes with local abundance, in salt marshes where its flower bearing stems can rise to 20 cm above a basal rosette of rounded leaves. Salt marshes pose the dual problem of high salinity and low oxygen levels. Both of these pose there own particular problems for L. humile, but the lack of oxygen to the root systems is possibly the greater of the two evils. It, along with other Limonium spp., overcome this problem by switching root respiration to a very high level of lactate fermentation, a protracted level much greater than the transient lactate glycolysis seen in most plants at the transition from normoxic to anoxic conditions (1). The lactate subsequently produced in the Limonium spp. root cells is of a degree that would lethally acidify them and is transported out of the cells into the environment, thus maintaining cell homeostasis.

Monday, September 19, 2011

As recently mentioned on this blog, its been a miserable summer sun-wise. Not so for a planet recently discovered by the Kepler spacecraft. Launched in March 2009, Kepler's aim is to find and analyse terrestrial and larger planets in or near the habitable zone of a wide variety of stars (1). And its come up with quite the find: a planet in orbit around two suns (2). Known as Kepler-16b, the Saturn sized planet describes a 229-day orbit around its two stars, which in turn eclipse each other. The stars are 20% and 69% the size of our own star, the sun, and have a 41 day orbit.

Kepler-16b (in blue) orbiting its two stars (orange and yellow).
Note that distances are not to scale

Wednesday, September 14, 2011

The sun has been in short supply in Ireland this year, and with September in full swing it looks (and feels) like we've had our, some may say inadequate, share for the year. These some would not include the Silver-washed Fritillary, Argynnis paphia. A large and attractive species native to Ireland that is common in woodlands, it has a yellow-orange upperwing marked with black that are similar to other Fritillary species, but is distinguished by the silvery sheen of the underwings (1). The adults are often found on their favourite food of brambles, basking in the sun. Here, they use their wings to absorb solar radiation and maintain their temperature above the ambient. By adjusting the angle of its wings at rest, it can absorb as much or as little sun as possible. Under artificial conditions, A. paphia was seen to adjust its wing position to maintain a thoracic temperature of 34±1.5 °C (3).

The Cormorant (Phalacrocorax carbo) is one of the largest seabirds in Ireland, and also one of the most familiar. It can often be seen feeding in estuaries and perched in trees, where they sometimes breed (1). With its dark body and long, hooked bill it could be mistaken for its relative the Shag (P. aristotelis). However, the Shag is a smaller bird by about 20 cm and is rarely seen inland. Adult Cormorants have an attractive blue-green sheen to their plumage, a yellow and white bare patch of skin on its face and a white thigh patch that disappears after the breeding season (1).

Cormorant, Phalacrocorax carbo

Recently, I observed a Cormorant perched on an old mooring post in a river estuary. It held its wings out from its body in a drooping fashion that is known as a spread-wing posture. Many birds engage in this type of behaviour. Cormorant feathers retain moisture when diving for food, which decreases buoyancy and aids underwater pursuit of prey. Only the outer layer of feathers are wettable however, and a a layer of insulating air is maintained next the skin when diving (2). Yet the outer feathers remain wet upon emergence and therefore need to be dried. Hence the spread-wing posture (as seen in the photographs) of the Cormorant, a living washing line.

The Common Darter (Sympetrum striolatum) is, as its name suggests, a common and widespread dragonfly in Ireland, indeed in Europe as a whole. Flying between June and October, it can often seen resting on paths or stones in sunny, open areas. S. striolatum is a very aggressive, territorial species and will “dart” at other, often larger dragonfly species. Males and females differ in their colouring, with mature males having orange-red, unwaisted abdomens in contrast to the the dull, yellow-brown females.

Female Common Darter, Sympetrum striolatum

Individuals are most often seen near favoured breeding sites of shallow ponds and small lakes, so it was therefore a surprise when in Hungry S. striolatum (along with five other species of Sympetrum) individuals were observed in large numbers in a cemetery that was nowhere near any water source (1). Were they just being spooky or was there a more rational answer?

Common Darter, Sympetrum striolatum

The dragonflies were seemingly attracted to polished black gravestones, where their behaviour was the same as if by water. This involved perching near the gravestones and defending their perch, flying individuals repeatedly touching the gravestone surfaces with their ventral sides and pairs in tandem position frequently circling over the gravestones. It was found that the gravestones reflect highly and horizontally polarised light in a manner almost identical to smooth water. S. striolatum, along with many other dragonfly species, find their aquatic habitats by means of polarotaxis, the use of reflected polarised light to discriminate between surfaces (2). This explains the attraction to the gravestones, an attraction that is so strong that females are sometimes lead to oviposit on the gravestones.

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